Ammonium sensing in the wheat pathogen Zymoseptoria tritici

Worldwide, wheat is the major source of vegetable protein in human food so it is essential that the supply of this food source is protected. Of concern are fungal pathogens that infect wheat and reduce agricultural yields. Z. tritici causes septoria tritici blotch disease that occurs throughout the world and can be a significant problem in developing countries. In severe epidemics wheat yields can be reduced by up to 50 %. Septoria tritici blotch disease is the most serious wheat disease in Europe and in the UK results in an annual loss of £50 million. Although several fungicides are used to control Z. tritici many populations have evolved fungicide resistance so that new fungicidal targets are needed. Understanding how morphological change is regulated in Z. tritici during its infection cycle will help in the development of new strategies to control this important pathogen. Fungi use ammonium as a preferred nitrogen source to synthesis essential metabolites. Ammonium also regulates fungal morphological change such as the dimorphic switch between yeast and filamentous growth. The conserved Mep2 ammonium transporter mediates ammonium sensing and is predicted to act analogous to a G-protein coupled receptor. We are currently studying ammonium sensing in the model yeast Saccharomyces cerevisiae and wish to further our understanding of fungal ammonium sensing by undertaking similar studies in the dimorphic fungal wheat pathogen Zymoseptoria tritici. Wheat is a current research focus of the BBSRC within its strategic priority of agriculture and food security . Mep2 homologues from plant pathogens act as ammonium sensors when expressed in S. cerevisiae consistent with the sensing role of Mep2 being widely conserved. Morphological change is an essential part of the infection cycle of many fungal plant pathogens. We will test the hypothesis that Mep2 in Z. tritici (ZtMep2) acts as an ammonium sensor to induce filamentous growth and that this process is required for the virulence of Z. tritici. The student will use a range of established molecular techniques to study ammonium metabolism, dimorphic growth and virulence of wild type and ZtMep2 lacking Z. tritici strains. Structural studies of ZtMep2 will also be undertaken to facilitate future functional analysis.